This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A majority of the population believes in the benefits of nutritional supplements and takes them regularly. Understanding the synergism between different components of supplements and the mechanisms of their effects are vital for rational use and recommendations. BCAA are unique in their ergogenic effects (ability to stimulate muscle growth, prevent muscle breakdown, and enhance exercise performance and recovery) and in their ability to enhance symptomatic relive of delayed onset muscle soreness (DOMS). The objective of this study will be to determine whether the addition of the dietary supplement B-alanine, a precursor of L-carnosine, to the BCAA regimen will increase the effects of the BCAA on the reduction of DOMS and in the enhancement of performance. We hypothesize that the addition of B-alanine to the BCAA regimen will enhance BCAA efficacy through an increase in L-carnosine levels in muscle leading to enhanced antioxidant and buffering capacity. In this study, one week of supplementation with BCAA with or without B-alanine will be tested to determine whether the combination attenuates, to a greater degree, the symptoms of DOMS and indices of muscle injury after an intense bout of eccentric exercise (downhill running test). Volunteers will be invited to participate in the study to be conducted on the University of Vermont (UVM) General Clinical Research Center (GCRC) at Fletcher Allen Health Care (FAHC). All volunteers will undergo a screening evaluation, including a physical fitness assessment using a graded exercise test. If the volunteer meets the eligibility criteria, he/she will be started on a daily dietary supplement of either BCAA alone or in combination with B-alanine. After 7 days, he/she will return to the GCRC for an overnight admission. During the supplementation period, the subject will be asked to keep a training log and to refrain from any vigorous exercise a day prior to admission for the exercise test. Upon arrival at the GCRC, a comprehensive evaluation of the training logs will be done in addition to obtaining a blood sample for pre-exercise levels of markers of oxidative stress and muscle injury. Pre-exercise baseline muscle soreness will also be assessed using a visual analog scale. The exercise test will consist of a 45 minute bout of downhill running on a motorized treadmill. After the exercise test is performed, blood samples and DOMS assessments will be obtained immediately after the exercise test and at 1, 6, 12, 18 and 24 hours post-exercise. Volunteers will be discharged the following day, 24 hours after the completion of the downhill running test and will return to the GCRC 72 hours after the exercise test for a final blood sample and DOMS assessment.